An apparatus and method for a reliable quantum signature. The method using the apparatus for a reliable quantum signature includes preparing a quantum signature by sharing a first secret key and a first Bell state with a signer's terminal device and by sharing a second secret key and a second Bell state with a verifier's terminal device; signing, by the signer's terminal device, a message with the quantum signature using a first encoding value, the first secret key, and the first Bell state; verifying, by the apparatus, the quantum signature of the message using the first encoding value, the first secret key, and the first Bell state; and finally verifying, by the apparatus, the quantum signature of the message using the verifier's terminal device, a second encoding value, a third encoding value, the second secret key, and the second Bell state.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method for a reliable quantum signature, in which an apparatus for a reliable quantum signature is used, comprising: preparing a quantum signature by sharing a first secret key and a first Bell state with a signer's terminal device and by sharing a second secret key and a second Bell state with multiple verifier's terminal devices; signing, by the signer's terminal device, a message m with the quantum signature using a first encoding value, the first secret key, and the first Bell state, wherein signing the message is configured such that the signer's terminal device calculates a first encoding value by performing a cryptographic operation on a hash value of the message and a first random bit string; verifying, by the apparatus, the quantum signature of the message using the first encoding value, the first secret key, and the first Bell state, wherein verifying the quantum signature is configured such that the apparatus calculates a second encoding value by performing a cryptographic operation on the hash value of the message, a third random bit string and a second random bit string obtained from the first encoding value; and finally verifying, by the apparatus, the quantum signature of the message using the verifier's terminal device, a second encoding value, third encoding values, the second secret key, and the second Bell state, wherein finally verifying the quantum signature is configured such that: the signer's terminal device confirms that the multiple verifier's terminal devices publishes the third encoding values and publishes the first random bit string after confirming publication of the third encoding values, and the apparatus finally verifies the quantum signature by checking whether a fourth encoding value, which is acquired by performing a cryptographic operation on the first random bit string and the third random bit string, and the third encoding values are the same.
2. The method of claim 1 , wherein each of the hash value and the first random bit string has a length of 2n and is configured with n groups by grouping bits thereof by two bits (n being a preset integer that is equal to or greater than 1).
3. The method of claim 2 , wherein verifying the quantum signature is configured such that the apparatus restores the first encoding value by receiving a first signature state for signing the message from the signer's terminal device and acquires a second random bit string using the hash value of the message.
4. The method of claim 3 , wherein verifying the quantum signature is configured to verify the quantum signature in such a way that the apparatus selects n bits from the second random bit string and checks whether the selected n bits match bits of the first random bit string that are located in same positions as the selected n bits.
5. The method of claim 4 , wherein each of the hash value of the message, the second random bit string and the third random bit string corresponds to remaining bits excluding bits located in same positions as the selected n bits.
6. The method of claim 5 , wherein finally verifying the quantum signature is configured such that one verifier's terminal device restores the second encoding value by receiving a second signature state for verifying the message from the apparatus and acquires a third encoding value using the hash value of the message from which the bits located in the same positions as the selected n bits are excluded.
7. The method of claim 6 , wherein the third encoding value is a result of a cryptographic operation performed on the second random bit string and the third random bit string, wherein each of the second random bit string and the third random bit string corresponds to remaining bits excluding bits located in same positions as the selected n bits.
8. The method of claim 1 , wherein each of the first random bit string and the third random bit string corresponds to remaining bits excluding bits located in same positions as the selected n bits.
10. The apparatus of claim 9 , wherein each of the hash value and the first random bit string has a length of 2n and is configured with n groups by grouping bits thereof by two bits (n being a preset integer that is equal to or greater than 1).
11. The apparatus of claim 10 , wherein the first quantum signature verification unit restores the first encoding value by receiving a first signature state for signing the message from the signer's terminal device and acquires a second random bit string using the hash value of the message.
12. The apparatus of claim 11 , wherein the first quantum signature verification unit verifies the quantum signature by selecting n bits from the second random bit string and checking whether the selected n bits match bits of the first random bit string that are located in same positions as the selected n bits.
13. The apparatus of claim 12 , wherein the second quantum signature verification unit calculates the second encoding value by performing a cryptographic operation on a hash value of the message, the second random bit string and a third random bit string, wherein each of the hash value of the message, the second random bit string and the third random bit string corresponds to remaining bits excluding bits located in same positions as the selected n bits.
14. The apparatus of claim 13 , wherein the second quantum signature verification unit transmits a second signature state for verifying the message to the verifier's terminal device, thereby requesting restoration of the second encoding value and acquisition of the third encoding value using the hash value of the message from which the bits located in the same positions as the selected n bits are excluded.
15. The apparatus of claim 14 , wherein the third encoding value is a result of a cryptographic operation performed on the second random bit string and the third random bit string, wherein each of the second random bit string and the third random bit string corresponds to remaining bits excluding bits located in same positions as the selected n bits.
16. The apparatus of claim 15 , wherein the second quantum signature verification unit confirms that the verifier's terminal device publishes the third encoding value and confirms that the signer's terminal device publishes the first random bit string after confirming publication of the third encoding value.
17. The apparatus of claim 16 , wherein the second quantum signature verification unit finally verifies the quantum signature by checking whether the third encoding value is equal to a fourth encoding value, which is acquired by performing a cryptographic operation on the first random bit string and the third random bit string, wherein each of the first random bit string and the third random bit string corresponds to remaining bits excluding bits located in same positions as the selected n bits.
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November 8, 2018
March 23, 2021
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